Method of welding tubular products of polyarylene sulfide and welded tubular structure

Abstract

A pair of tubular products of polyarylene sulfide having end faces to be welded are welded to each other by heating the end faces by a hot plate in no contact with the end faces to a surface temperature which is at least the melting heat-absorption peak temperature and at most 80 DEG C. above the melting initiation temperature of the polyarylene sulfide, and abutting the end faces under a pressure of 50-1500 kPa when the end faces are at a surface temperature which is at least 10 DEG C. above the melting initiation temperature and not exceeding the melting heat-absorption peak temperature of the polyarylene sulfide. As a result, a welded tubular structure having a weld with a small inside bead but having a sufficiently large weld strength can be obtained with substantially no thermal degradation and at a good operating efficiency.

What is claimed is: 
     
       1. A method of welding tubular products of polyarylene sulfide, comprising the steps of: providing a pair of tubular products of polyarylene sulfide having end faces to be welded to each other, the polyarylene sulfide showing a melting initiation temperature and a melting heat-absorption peak temperature,   heating the end faces by a hot plate in no contact with the end faces, and   abutting the end faces under pressure when the end faces are at a surface temperature for abutting which is at least 10° C. above the melting initiation temperature and is not exceeding the melting heat-absorption peak temperature, respectively, of the polyarylene sulfide, thereby forming a weld.   
     
     
       2. A method according to claim 1, wherein the end faces are heated to a surface temperature which is at least the melting heat-absorption peak temperature and at most 80° C. above the melting heat-absorption peak temperature, respectively, of the polyarylene sulfide, the hot plates is then moved away from the end faces, thereby to allow the end faces to cool to the surface temperature for abutting, and then the end faces are abutted to each other at a pressure of about 50 to 1500 kPa (0.5-15 kg/cm 2 ). 
     
     
       3. A method according to claim 1, wherein each end of the tubular products to be welded is provided with an inside taper by cutting inside edge and then subjected to the heating and abutting. 
     
     
       4. A method according to claim 1, wherein each end of the tubular products to be welded is provided with an inside taper by cutting inside edge to leave an end face having a thickness of at least 1/3 of that of the tubular product per se, and the inside taper shows an inside taper angle of 10-70 degrees with respect to the end face. 
     
     
       5. A method according to claim 4, wherein the inside taper angle is 20-60 degrees. 
     
     
       6. A method according to claim 1, wherein the end faces are abutted under pressure when the end faces are at a surface temperature which is at least 15° C. above the melting initiation temperature and is at least 2° C. below the melting heat-absorption peak temperature, respectively, of the polyarylene sulfide. 
     
     
       7. A method according to claim 2, wherein the end faces are abutted to each other at a pressure of about 70 to 1200 kPa (0.7-12 kg/cm 2 ).